PLEASE NOTE: Advanced Physics Equipment is built-upon-order. We do not stock these items in house, but order them built when an order is placed. Build orders take approximately 90 days.

• Study electron photoemission from a metal surface

• Obtain the characteristic curves of a vacuum photocell

• Explore the effect of illumination intensity using the inverse square law

The Photoelectric Effect Apparatus allows the photoelectric emission from a mixed metal cathode in vacuum to be studied. It consists of a light-tight box connected to a control and measurement unit by shielded cables.

The light-tight box contains a vacuum phototube with a Cs/Sb cathode and a current-controlled incandescent lamp mounted on a slide operated from outside the box to vary the illumination of the phototube.

The control and measurement unit contains an adjustable highly stabilized lamp power supply. The current is indicated on a three-digit display. A second, independent, highly stabilized voltage source controlled by a multi-turn potentiometer applies a precise dc extraction voltage to the phototube electrodes. The applied voltage is indicated on a three-digit display. The resulting photocurrent is measured by a sensitive amplifier and indicated on a 3-1/2-digit display.

The apparatus shows the linear relation between light intensity and emission current and demonstrates the space charge dominated and saturation regions of the emission current relationship to the extraction voltage.

The control and measurement unit contains a highly stabilized lamp power supply adjusted by a multi-turn potentiometer.